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Immunotherapy: In a Nutshell, Possible Treatment for Peanut Allergy

When our youngest daughter was a year old, we decided to introduce her to some more interesting table foods. One night at dinner, I gave her a spoonful of chicken cooked with ginger, soy sauce, brown sugar, and peanut butter. I thought she might protest. What I didn’t expect were swollen cheeks and husky breathing.

Minutes later, lights flashed in our driveway and half a dozen men in blue crammed into our living room to check our daughter’s vital signs. I was relieved, if a bit sheepish: No treatment was needed after all. But later tests revealed a mild to moderate peanut allergy, and so we joined the ranks of Epi-Pen-toting parents.

Currently there is no approved treatment for peanut allergy. As a result patients or their parents must carefully monitor diets and carry around lifesaving doses of epinephrine (used in cases of accidental ingestion to treat a severe allergic reaction, or anaphylaxis). However, a recent double-blind, multicenter study (reported here in The Journal of Allergy and Clinical Immunology) shows that sublingual immunotherapy might be a way to prevent allergic reactions.

In 20 percent of cases, Burks explains, children who acquire a peanut allergy in the first years of life will eventually outgrow it. But it’s hard to predict who will leave the allergy behind, or what will be the severity of side effects. “There’s certainly anxiety inherent in a diagnosis because of the [uncertaity] of what future reactions might be like,” says Burks.

“The prevalence of peanut allergies has changed so much in the last two decades that it has become more important to find a treatment,” he adds. “Only recently though has [sublingual immunotherapy (or SLIT)] been used with appropriate dosing that could be used for peanut allergy.” (SLIT has previously been used to treat a range of allergies, from milk to peaches.)

SLIT works by desensitizing the patient to the allergen over time. In this study, patients were exposed over many weeks to tiny (and gradually increasing) daily doses of peanut powder in a liquid that was squirted into the mouth and held under the tongue for two minutes before swallowing. That time in the mouth is key, explains Burks, because mucous membranes there give the allergen rapid entry into the body’s immune system.

(Subcutaneous immunotherapy, which uses injections, is another treatment option for some kinds of allergies, but it has not been found to be safe in the case of peanut. According to Burks, studies were stopped in the 1990s because of significant side effects.)

At the beginning of the SLIT study Burks took part in, 40 subjects with peanut allergy were given an oral food challenge of up to 2 grams of peanut powder to see how much they could tolerate. Then subjects were randomly assigned to receive either peanut SLIT or a placebo. At the end of a 44-week period, the patients were given another food challenge. Those who could safely consume 5 g, or at least 10-fold more peanut powder compared to their baseline, were considered “responders.” In the SLIT group, 70 percent were responders, compared to just 15 percent of the placebo group. Among responders, the median consumption of peanut powder rose from 3.5 to 496 milligrams. Following 68 weeks of treatment, median consumption climbed to 996 milligrams, or about the equivalent of three peanuts.

That doesn’t sound like much (and indeed, immunotherapy is no invitation to start snacking on Snickers bars). But it’s significant to allergy sufferers. According to Burks, an allergic reaction typically happens to less than one third of a peanut. (Trace amounts can find their way into foods prepared in factories, kitchens, or restaurants where peanuts are used. “In theory, you could take a daily dose and it could protect you from most accidental interactions,” he says.

“What we don’t know is the dosing ranges and how long to treat someone to make it permanent—or even if we can make it permanent,” Burks adds. “What needs to happen are more studies, using more people, in different dosing regimens.”